首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   163096篇
  免费   10377篇
  国内免费   1262篇
耳鼻咽喉   2272篇
儿科学   3088篇
妇产科学   3749篇
基础医学   24164篇
口腔科学   3374篇
临床医学   15518篇
内科学   31168篇
皮肤病学   4389篇
神经病学   12124篇
特种医学   8382篇
外科学   21956篇
综合类   2184篇
现状与发展   5篇
一般理论   81篇
预防医学   9769篇
眼科学   4321篇
药学   13709篇
  36篇
中国医学   1604篇
肿瘤学   12842篇
  2024年   337篇
  2023年   1159篇
  2022年   2768篇
  2021年   4931篇
  2020年   2592篇
  2019年   3595篇
  2018年   4422篇
  2017年   3234篇
  2016年   4196篇
  2015年   5648篇
  2014年   6921篇
  2013年   8404篇
  2012年   12662篇
  2011年   12287篇
  2010年   7279篇
  2009年   6116篇
  2008年   9271篇
  2007年   9169篇
  2006年   8396篇
  2005年   7994篇
  2004年   7128篇
  2003年   6195篇
  2002年   5385篇
  2001年   4390篇
  2000年   4040篇
  1999年   3282篇
  1998年   1378篇
  1997年   1067篇
  1996年   1048篇
  1995年   921篇
  1994年   807篇
  1993年   693篇
  1992年   1588篇
  1991年   1584篇
  1990年   1373篇
  1989年   1272篇
  1988年   1189篇
  1987年   1063篇
  1986年   1054篇
  1985年   922篇
  1984年   652篇
  1983年   577篇
  1982年   412篇
  1981年   386篇
  1980年   348篇
  1979年   527篇
  1978年   417篇
  1977年   397篇
  1976年   355篇
  1974年   360篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
This study examined the effects of cognitive-behavioral group therapy (CBT) on the self-esteem, depression, and self-efficacy of runaway adolescents residing in a shelter in Seoul, South Korea. The study used a control group pretest-posttest design. The experimental group and the control group consisted of 14 and 13 male subjects, respectively, with subjects having been randomly assigned to these groups. The experimental group participated in a CBT that consisted of eight sessions over an 8-week period; the control group did not participate in the program. To examine the effects of the CBT on dependent variables, the Wilcoxon signed rank test was used. The scores on depression decreased significantly (z = -2.325, p = .02) and those on self-efficacy increased significantly (z = -2.098, p = .03) after the intervention in the experimental group. There was no significant change on self-esteem (z = -1.19, p = .23). In the control group, the scores on depression, self-esteem, and self-efficacy did not change significantly after the intervention period. The CBT developed in this study consisted of structured and specific content that could be usefully applied to runaway adolescents residing in a shelter.  相似文献   
72.
To evaluate noninvasive measures of gene expression and tumor response in a gene-dependent enzyme prodrug therapy (GDEPT), a bifunctional fusion gene between Saccharomyces cerevisiae cytosine deaminase (CD) and Haemophilus influenzae uracil phosphoribosyltransferase (UPRT) was constructed. CD deaminates 5-fluorocytosine (5FC) to 5-fluorouracil (5FU), and UPRT subsequently converts 5FU to fluorouridine monophosphate, and both of these reactions can be monitored noninvasively in vitro and in vivo using 19F magnetic resonance spectroscopy (MRS). Following transient transfection the CD-UPRT fusion protein exhibited both UPRT and CD enzymatic activities as documented by 19F MRS. In addition, an increase in CD activity and thermal stability was witnessed for the fusion protein compared to native CD. Stable expression of CD-UPRT in 9L glioma cells increased both 5FC and 5FU sensitivity in vitro compared to CD-expressing and wild-type 9L cells. Noninvasive 19F MRS of both CD and UPRT gene function in vivo demonstrated that in animals bearing CD-expressing tumors there was limited conversion of 5FC to 5FU with no measurable accumulation of cytotoxic fluorinated nucleotides (F-nucs). In contrast, CD-UPRT-expressing tumors had increased CD gene activity with a threefold higher intratumoral accumulation of 5FU and significant generation of F-nucs. Finally, CD-UPRT yielded increased efficacy in an orthotopic animal model of high-grade glioma. More importantly, early changes in cellular water mobility, which are felt to reflect cellular death, as measured by diffusion-weighted MRI, were predictive of both durable response and increased animal survival. These results demonstrate the increased efficacy of the CD-UPRT GDEPT compared to CD alone both biochemically and in a preclinical model and validate both 19F MRS and diffusion-weighted MRI as tools to assess gene function and therapeutic efficacy.  相似文献   
73.
74.
75.
Most lesions in FD and their attendant functional disability occur within the first decade; 90% of lesions are present by 15 years, and the median age when assistive devices are needed is 7 years. These findings have implications for prognosis and determining the timing and type of therapy. INTRODUCTION: Fibrous dysplasia of bone (FD) is an uncommon skeletal disorder in which normal bone is replaced by abnormal fibro-osseous tissue. Variable amounts of skeletal involvement and disability occur. The age at which lesions are established, the pace at which the disease progresses, if (or when) the disease plateaus, and how these parameters relate to the onset of disability are unknown. To answer these questions, we performed a retrospective analysis of a group of subjects with FD. MATERIALS AND METHODS: One hundred nine subjects with a spectrum of FD were studied for up to 32 years. Disease progression was assessed in serial (99)Tc-MDP bone scans by determining the location and extent of FD lesions using a validated bone scan scoring tool. Physical function and the need for ambulatory aids were assessed. RESULTS: Ninety percent of the total body disease skeletal burden was established by age 15. Disease was established in a region-specific pattern; in the craniofacial region, 90% of the lesions were present by 3.4 yr, in the extremities, 90% were present by 13.7 yr, and in the axial skeleton, 90% were present by 15.5 yr. Twenty-five of 103 subjects eventually needed ambulatory aids. The median age at which assistance was needed was 7 yr (range, 1-43 yr). The median bone scan score for subjects needing assistance was 64.3 (range, 18.6-75) compared with 23.1 (range, 0.5-63.5) in the unassisted subjects (p < 0.0001). Among subjects needing assistance with ambulation, 92% showed this need by 17 yr. CONCLUSIONS: The majority of skeletal lesions and the associated functional disability occur within the first decade of life. The implication is that the window of time for preventative therapies is narrow. Likewise, therapeutic interventions must be tailored to where the patient is in the natural history of the disease (i.e., progressive disease [young] versus established disease [older subjects]). These findings have implications for prognosis, the timing and type of therapy, and the development of trials of new therapies and their interpretation.  相似文献   
76.
The FIGNL1 gene was proven to be a new subfamily member of ATPases associated with diverse cellular activities (AAA proteins). In this in vitro study, the AAA proteins inhibited osteoblast proliferation and stimulated osteoblast differentiation. We showed that FIGNL1 may play some regulatory role in osteoblastogenesis. INTRODUCTION: The fidgetin-like 1 (FIGNL1) gene encodes a new subfamily member of ATPases associated with diverse cellular activities (AAA proteins). Although the FIGNL1 protein localizes to both the nucleus and cytoplasm, the function of FIGNL1 remains unknown. In a previous study, we identified several genes that mediate the anabolic effects of basic fibroblast growth factor (bFGF) on bone by using microarray data. FIGNL1 was one of the genes that downregulated >2-fold in MC3T3-E1 cells after treatment with bFGF. Therefore, this study was aimed to identify and confirm the function of FIGNL1 on osteoblastogenesis. MATERIALS AND METHODS: We examined the effect of the FIGNL1 gene on proliferation, differentiation, and apoptosis in mouse osteoblast cells (MC3T3-E1 and mouse primary calvarial cells) using flow cytometry, RT-PCR, cell proliferation assay, and cell death assay. MC3T3-E1 cells and mouse calvarial cells were transfected with small interfering RNA (siRNA) directed against the FIGNL1 or nontargeting control siRNA and examined by cell proliferation and cell death assays. Also, FIGNL1 was fused to enhance green fluorescent protein (EGFP), and the EGFP-fused protein was transiently expressed in MC3T3-E1 cells. RESULTS: Reduced expression of FIGNL1 by bFGF and TGF-beta1 treatment was verified by RT-PCR analysis. Overexpression of FIGNL1 reduced the proliferation of MC3T3-E1 and calvarial cells, more than the mock transfected control cells did. In contrast, siFIGNL1 transfection significantly increased the proliferation of osteoblasts, whereas overexpression of FIGNL1 did not seem to alter apoptosis in osteoblasts. Meanwhile, overexpression of FIGNL1 enhanced the mRNA expression of alkaline phosphatase (ALP) and osteocalcin (OCN) in osteoblasts. In contrast, siFIGNL1 decreased the expression of ALP and OCN. A pEGFP-FIGNL1 transfected into MCT3-E1 cells had an initially ubiquitous distribution and rapidly translocated to the nucleus 1 h after bFGF treatment. CONCLUSIONS: From these results, we proposed that FIGNL1, a subfamily member of the AAA family of proteins, might play some regulatory role in osteoblast proliferation and differentiation. Further analyses of FIGNL1 will be needed to better delineate the mechanisms contributing to the inhibition of proliferation and stimulation of osteoblast differentiation.  相似文献   
77.
A mushroom extract, Agaricus blazei Murill Kyowa (ABMK), has been reported to possess antimutagenic and antitumor effects. Here, we investigate the beneficial effects of ABMK consumption on immunological status and qualities of life in cancer patients undergoing chemotherapy. One hundred cervical, ovarian, and endometrial cancer patients were treated either with carboplatin (300 mg / m(2)) plus VP16 (etoposide, 100 mg / m(2)) or with carboplatin (300 mg / m(2)) plus taxol (175 mg / m(2)) every 3 weeks for at least three cycles with or without oral consumption of ABMK. We observed that natural killer cell activity was significantly higher in ABMK-treated group (ANOVA, n = 39, P < 0.002) as compared with nontreated placebo group (n = 61). However, no significant difference in lymphokine-activated killer and monocyte activities was observed in a manner similar to the count of specific immune cell populations between ABMK-treated and nontreated groups. However, chemotherapy-associated side effects such as appetite, alopecia, emotional stability, and general weakness were all improved by ABMK treatment. Taken together, this suggests that ABMK treatment might be beneficial for gynecological cancer patients undergoing chemotherapy.  相似文献   
78.
79.
80.
The relationship of large and vascularized chorioangiomas to adverse pregnancy outcome is well recognized. We present a patient with a large placental tumor and signs of impending fetal cardiac failure. The angioarchitecture of the tumor depicted by three-dimensional (3D) power Doppler ultrasound enabled us to accurately diagnose a placental chorioangioma. During the follow-up period, quantitative flow data obtained using 3D power Doppler indicated altered hemodynamics in the tumor and concomitant improvement in the condition of the fetus, enabling us to manage the mother conservatively. Spontaneous delivery occurred at 38 weeks without any complications. This report demonstrates the potential value of 3D power Doppler in prenatal diagnosis and monitoring of pregnancies complicated by large, vascularized chorioangioma.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号